205 
one will understand that, if lie were presented with a 
drawing of a plant bounded by rectilinear outlines, or of an 
animal forming an exact cube, such professed likeness 
was an unnatural impossibility. Freedom of development 
comes in place of mathematical law, and with this freedom 
beauty and variety appear. 
In order to attain these results (apparently), the spiral takes 
the place of the straight line. Even in the growth of the upright 
stem of a tree we may notice that spiral tendency, which is 
still more evident in the set of leaves on a plant, or in the 
arrangement of the parts in the cone of a fir. Cells with 
spiral cell-walls originate a vessel with spiral walls; these 
vessels twine in a certain direction and produce a spiral 
stem.* The stem itself may twine around another tree in 
a spiral manner; leaves, flowers, fruit, may be arranged in 
spirals of various orders. The shell of the .nautilus is rolled 
up in a most graceful spiral ; the heart of mammals is a 
double continuous spiral of exquisite beauty. The wings of 
birds, and the extremities of bipeds and quadrupeds, are dis- 
tinctly spiral in their nature, and their movements are curved 
spiral movements ; nay, more, the vertebral column itself 
is a spiral of very unusual but delightful curve. Dutrocliet 
states that there is a revolving movement in the summits 
of stems, — a spiral rolling of the stems round their supports, 
a torsion of the stems upon themselves, and a spii'al arrange- 
ment of leaves; all these being in each plant in the same 
direction. These phenomena, he avers, are owing to an 
internal vital force, which causes a revolution round the central 
axis of the stem. “ The heart pulsates while yet a solid mass, 
and before it contains blood” f Thus we continually touch 
upon the verge of the unknown. The very plants that twine 
around our hedges present problems which pass all the boun- 
daries of science. When we come to speak of voluntary 
motion (as in Desmodium (jyrans), of what in animals would 
be termed instinct, of extraordinary sensibility to impressions 
in mere plants, amounting to their recoiling with disgust from 
some objects and attaching themselves to others, it is obvious 
* Pettigrew, Physiology of the Circulation , p. 17, note. A good illustra- 
tion of spiral cells may be seen in Plate III. of my Quinology of the East 
Indian Plantations, a copy of which work I have presented to the Institute. 
In Plate II. may also be seen a drawing of the fibres of the liber, having a 
similar spiral formation, seen very beautifully under the microscope, 
f Id., p. 127. 
VOL. XII. 
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